Thermostable physically crosslinked cryogel from carboxymethylated konjac glucomannan fabricated by freeze-thawing. (January 2022)

• Record Type: Journal Article
• Authors: Guo, Yalong; Wu, Min; Li, Ruiqi; Cai, Zhixiang; Zhang, Hongbin
• Is Part Of: Food hydrocolloids. Volume 122(2022)
• Publication Date: 2022-01
• Subjects: Carboxymethyl konjac glucomannan -- Freeze-thaw technique -- Cryogel -- Rheological properties -- Gelation mechanism; Hydrocolloids -- Periodicals; Food additives -- Periodicals; Colloïdes -- Périodiques; Aliments -- Additifs -- Périodiques; Colloids; Food additives; Periodicals; Electronic journals; 664.06
• DOI: 10.1016/j.foodhyd.2021.107103
• Languages: English
• ISSNs: 0268-005X

Abstract

Abstract : Physically crosslinked cryogels of carboxymethylated konjac glucomannan (CMKGM) with different molecular weights ( M w, 1.57 × 10 5 –7.33 × 10 5 Da) and degrees of substitution (DS, 0.19–1.63) were fabricated by using the freeze-thaw technique. The acidification of CMKGM solution at a sufficiently low pH of 1.0 is a prerequisite to produce a cryogel. Both the M w and DS of CMKGM significantly affected the formation and mechanical strength of the cryogels. A high DS value cannot ensure the formation of the cryogel when the M w of CMKGM is not sufficiently high. While the cryogel from CMKGM with the highest M w of 7.33 × 10 5 Da and lowest DS of 0.19 exhibited the highest gel strength, cryogels could not be effectively formed for CMKGM with a DS beyond 1 and M w below 2.24 × 10 5 Da. Furthermore, the gel strength could be enhanced by increasing polysaccharide concentration, freezing time, and the number of freeze-thaw cycles or thawing at a moderate temperature (25 °C). It was demonstrated that the intermolecular multiple hydrogen bonding was the major driving force in the formation of CMKGM cryogels with negligible, if any, participation of crystalline ordered structures. Detailed hydrogen bonding patterns in the gel network were proposed. In acidic cryogels, there existed three types of hydrogen bonds formed by –COOH and –OH groups, whereas in neutral cryogels, two kinds of hydrogen bonding among -COO - and –OH groups were involved. The intermolecular multiple hydrogen bonding endows the physical hydrogels with excellent thermostability. Graphical abstract: Image 1 Highlights: Physical hydrogels of CMKGM were fabricated by using freeze-thaw technique. DS of CMKGM substantially affected the formation and gel strength of the cryogels. Gel strength is tunable by varying polymer concentration and gelling conditions. The cryogelation is due to different types of intermolecular multiple hydrogen bonding. Different hydrogen bonding patterns in acidic and neutral cryogels were proposed.